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%I #9 Sep 16 2015 04:40:23
%S 1,1,1,3,1,1,12,16,1,17,31,31,25,1,52,52,52,61,47,23,91,102,102,114,
%T 114,127,1,103,169,184,184,200,1,1,251,269,115,1,326,346,1,155,409,
%U 431,1,1,1,143,525,550,1,1,602,629,101,37,463,1,753,783,783,814,89,585,910,943
%N a(n) = largest proper divisor of the sum of all positive integers which are <= n and are not included among the first n-1 terms of the sequence.
%e The positive integers which are <= 8 and do not occur among the first 7 terms of the sequence are 2,4,5,6,7,8. a(8) is the largest proper divisor of the sum of these integers. 2+4+5+6+7+8 = 32. So a(8) is the largest proper divisor of 32, which is 16.
%t a = {1}; For[n = 2, n < 70, n++, AppendTo[a, Divisors[n*(n + 1)/2 - Plus @@ Select[Union[a, a], # < n + 1 &]][[ -2]]]]; a (* _Stefan Steinerberger_, Nov 21 2007 *)
%K nonn
%O 1,4
%A _Leroy Quet_, May 30 2007
%E More terms from _Stefan Steinerberger_, Nov 21 2007
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